1. Field of the Invention
The present invention relates to a process and apparatus for the prestacking of sheets in a sheet feeder of a rotary printing press, the printing press being provided with lateral stack stops that can be adjusted to the size of the sheet format to be processed, and the printing press having an automatic lateral stacking orientation apparatus and a stack raising apparatus.
2. Background Information
DE 27 50 105 A1 and EP 0 253 165 B1 disclose sheet feeders having lateral stops for the sheet stack that can be adjusted by means of servomotors to the size of the sheet format to be printed. The stack stops can be used, for example, to perform a pre-orientation of the sheets to be printed. In addition, the lateral stops can also be used to orient improperly stacked sheets in the upper area, in order to transport the individual sheets in a desired lateral position to the sheet feeder. For this purpose, it is necessary to accurately adjust the lateral stops to the current paper format, which requires that the individual paper layers be formed, outside of the press, into a sheet stack, which is then introduced into the sheet feeder. The heavy sheet stack must thereby be very precisely oriented laterally, so that, when it is raised by the stack raising device, it does not collide with the lateral stack stops.
DE 29 11 735 A1 shows feeler rollers which emit a control signal which is used for the automatic lateral orientation of the sheet stack. An electric motor moves the sheet stack in one direction or the other, so that the top layers of the sheet stack, in their lateral position, coincide with the stack stops.
One disadvantage of these embodiments of the prior art is that the sheet stack can only be filled up outside the press, because the lateral stack stops act only on the top layers of the sheet stack. If the printer, for purposes of prestacking, wants to fill up the sheet stack in the press, he must first lower the sheet stack, to get sufficient space to insert the sheet stack. Then he would not be able to straighten them laterally, so that only with considerable effort could he achieve a perpendicular sheet stack with a uniform lateral position of the sheets.